Re: Meanwhile, on Windows 7...
... KB4056894 is the Win7 version of KB4056892. The details of **94 state Security updates to Windows SMB Server, Windows Kernel, Microsoft Graphics Component, Internet Explorer, and Windows Graphics. The notes mention the same registry key details. **94 installs automatically, and leaves one laptop with a STOP error seconds after trying to start Windows.
Solutions mostly involved the Windows Repair tool, which auto-recovered one time (2nd or 3rd), but required two system restores on a later fix, which is why the December Quality Roll-up reappeared - I'd applied that one late and restores after that date failed to stick.
YMMV, but that's been my experience so far with this out of step patch.
From a Meltdown perspective, it's an older laptop (Toshiba SatPro A300D) running an AMD Turion64 X2 CPU, and Radeon graphics. I haven't tried other Intel/Nvidia and Intel/Intel laptops yet, Win10 or Win7-32bit may also have a different ride, which might also be affected by the rest of my PCs running different AV - the A300D really stands apart from the others.